Various etching processes are utilized in the fabrication of semiconductor devices. Such etching processes are utilized to control and maintain critical dimensions of various device structures, such as, for example, transistors, capacitors, and interconnects. As semiconductor devices become more integrated and miniaturized, the maintenance and control of such critical dimensions of device structures become more important.
At least one goal of an etch process in the fabrication of devices is to be able to reproduce the features of a mask used in the etching process together with control of the etched features. For example, etches are typically highly selective to the film or layer under the material being etched. Further, for example, dry etching can provide more control of the. etched features, relative to wet etching, as dry etching can be performed in an anisotropic and/or isotropic manner as opposed to isotropic wet etching.
One or more anisotropic and isotropic etching steps can be performed to control the etching of different device features. However, when etching device features, such as, for example, the etching of conductive material on vertical or near vertical (e.g., substantially vertical) sidewalls of a device structure, problems may occur from the use of anisotropic etching steps. For example, an anisotropic etch, may be used to remove a bulk of conductive material formed over a device structure having substantially vertical sidewalls as one step in patterning the conductive material. Such an anisotropic etch of the conductive material leaves a blocking material over the vertical or near vertical sidewalls which are to be etched, such as, a carbon based polymer material formed at least in part from etching of the photoresist used for such patterning. The blocking material inhibits the later use of an isotropic etch to remove the conductive material under the blocking material from the substantially vertical sidewalls. As a result of the inhibition of the isotropic etch to remove conductive material from the substantially vertical sidewalls,. undesired conductive material, i.e. stringers, are left behind at the sidewalls.
Therefore, there is a need in the art for etching methods that allow for adequate removal of material, such as, for example, conductive material, from the substantially vertical sidewalls of a device structure during fabrication of semiconductor devices. The present invention provides such a method overcoming the problems as described above and others that will be readily apparent to one skilled in the art from the description of the present invention below.